Effects of kangaroo mother care on maternal and paternal health: systematic review and meta-analysis

Abstract Objective To investigate the effect of kangaroo mother care for low-birth-weight and preterm infants on parents’ mental and physical health. Methods The Cochrane Central Register of Controlled Trials, Cochrane Register of Studies Online, PubMed®, Web of Science, Scopus and EMBASE® databases were searched on 16 January 2023 for randomized and quasi-randomized trials on kangaroo mother care. Records identified were screened independently by two reviewers. Pooled relative risks (RRs) are reported for categorical variables, and standardized mean differences (SMDs) or mean differences are reported for continuous variables. Evidence quality was assessed using the GRADE approach. Findings The search identified 30 studies involving 7719 preterm or low-birth-weight infants. There was high-certainty evidence that kangaroo mother care substantially reduced the risk of moderate-to-severe postpartum maternal depressive symptoms compared with no kangaroo mother care (RR: 0.76; 95% confidence interval, CI: 0.59 to 0.96). In addition, there was low-certainty evidence that kangaroo mother care reduced scores for maternal stress (SMD: −0.82; 95% CI: −1.32 to −0.32) and anxiety (SMD: −0.62; 95% CI: −1.01 to −0.23) and increased mother–infant attachment and bonding scores (SMD: 1.19; 95% CI: 0.27 to 2.10). Limited evidence indicated father–infant interactions may be improved, though no marked effect on paternal depression or stress was observed. No trial reported parental physical health outcomes. Conclusion Kangaroo mother care for preterm and low-birth-weight infants was associated with less postpartum maternal depression, stress and anxiety and better mother–infant attachment and bonding. More research is required to evaluate effects on paternal health.


Introduction
Pregnancy and childbirth are critical periods in women's lives involving major physiological, psychological, domestic and sociodemographic changes. During the first 6 months postpartum, 1 an estimated 15% to 33% of mothers experience anxiety and, during the first year after birth, around one fifth have postpartum depressive symptoms. 2 The prevalence of depressive symptoms and anxiety seems to be even higher among mothers whose infants are born preterm (i.e. under 37 weeks' gestation) or have a low birth weight (i.e. under 2500 g) compared to those whose infants are born at full term and have a normal birth weight. [3][4][5] In addition, the birth of a preterm or low-birth-weight baby can also have consequences for the father's mental health and have a negative impact on family life. 5,6 Kangaroo mother care is an intervention that involves continuous skin-to-skin contact of the infant with the mother's chest (or the chest of another caregiver when the mother is unavailable) and exclusive breastfeeding. The World Health Organization (WHO) recommends early and prolonged kangaroo mother care for low-birth-weight and preterm infants as it has been shown to reduce the risk of neonatal and infant death and to prevent infection. [7][8][9] Although the beneficial effects of the intervention on infant health have been reviewed rigorously, 8,9 its potential benefits for mothers and fathers are less well understood, which often presents a barrier to the promotion of kangaroo mother care. 10 Previous reviews of the effect of kangaroo mother care on maternal health outcomes have either not involved a meta-analysis (i.e. no pooled estimates), 11 been limited to only specific health outcomes (e.g. the mean maternal depression score), 12 or not included all preterm and low-birth-weight infants. 13 In addition, these reviews have not reported paternal health outcomes. There is a need, therefore, for a rigorous and updated evidence synthesis that comprehensively summarizes the full range of benefits provided by kangaroo mother care for both maternal and paternal health. This information will be important for updating recommendations for kangaroo mother care that reflect improvements in maternal health in addition to benefits for the child.
The primary aim of our study was to supplement existing knowledge on kangaroo mother care by performing a comprehensive and up-to-date literature review and meta-analysis of the impact of kangaroo mother care for low-birth-weight and preterm infants on the mothers' mental and physical health. In addition, we investigated the effect of the practice on bonding between mother and infant and on paternal mental and physical health. We also conducted a quality assessment using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to evaluate the certainty of the pooled estimates, 14 which has not been done in any prior systematic review.

Methods
We searched the Cochrane Central Register of Controlled Trials (CENTRAL), Cochrane Register of Studies Online, PubMed ® , Web of Science™, Scopus and EMBASE ® databases for articles on randomized controlled trials or quasi-randomized trials published before 16 January 2023 that compared kangaroo mother care with no kangaroo mother care for preterm or lowbirth-weight infants. Details of the search strategies are provided in Box 1. There were no date or language restrictions in the search strategy. Articles written in a language other than English were reviewed and data were extracted from the English abstract where available. If an abstract was not in English, an online translation application was used. If it was still not possible to extract the Objective To investigate the effect of kangaroo mother care for low-birth-weight and preterm infants on parents' mental and physical health. Methods The Cochrane Central Register of Controlled Trials, Cochrane Register of Studies Online, PubMed ® , Web of Science, Scopus and EMBASE ® databases were searched on 16 January 2023 for randomized and quasi-randomized trials on kangaroo mother care. Records identified were screened independently by two reviewers. Pooled relative risks (RRs) are reported for categorical variables, and standardized mean differences (SMDs) or mean differences are reported for continuous variables. Evidence quality was assessed using the GRADE approach. Findings The search identified 30 studies involving 7719 preterm or low-birth-weight infants. There was high-certainty evidence that kangaroo mother care substantially reduced the risk of moderate-to-severe postpartum maternal depressive symptoms compared with no kangaroo mother care (RR: 0.76; 95% confidence interval, CI: 0.59 to 0.96). In addition, there was low-certainty evidence that kangaroo mother care reduced scores for maternal stress (SMD: −0.82; 95% CI: −1.32 to −0.32) and anxiety (SMD: −0.62; 95% CI: −1.01 to −0.23) and increased mother-infant attachment and bonding scores (SMD: 1.19; 95% CI: 0.27 to 2.10). Limited evidence indicated father-infant interactions may be improved, though no marked effect on paternal depression or stress was observed. No trial reported parental physical health outcomes. Conclusion Kangaroo mother care for preterm and low-birth-weight infants was associated with less postpartum maternal depression, stress and anxiety and better mother-infant attachment and bonding. More research is required to evaluate effects on paternal health. relevant information, the article was excluded. In addition, the reference lists of the articles selected were searched manually to identify further relevant articles. This review was registered in the PROSPERO prospective register of systematic reviews (CRD42022323152) in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocol. 15 We included studies that defined kangaroo mother care as skin-toskin contact accompanied by the promotion of, or support for, exclusive breastfeeding. Kangaroo mother care could be initiated in either a hospital or a community setting, and could be initiated either immediately after birth or when low-birth-weight or preterm infants were in a stable condition. We excluded observational and crossover trials, and trials involving infants born at full term or with a normal birth weight.
The primary outcomes studied were maternal mental health outcomes, i n c l u d i n g m o d e r at e o r s e v e r e postpartum depressive symptoms, and scores for postpartum depressive symptoms, stress, anxiety and distress. Secondary outcomes included: motherinfant attachment and bonding scores; paternal mental health outcomes; and maternal physical health outcomes such as breast problems (e.g. abscess or engorgement), postpartum bleeding and uterine involution. All outcomes were reported at the latest follow-up. D a t a w e r e r e v i e w e d u s i n g Covidence systematic review software (Veritas Health Innovation, Melbourne, Australia). Two authors independently screened titles and abstracts to identify relevant citations before carrying out full text reviews using predefined inclusion criteria. Data were extracted using a modified version of the Cochrane Effective Practice and Organization of Care (EPOC) group data collection checklist (Cochrane EPOC Group, London, United Kingdom of Great Britain and Northern Ireland), 16 and included study identifiers and context, study design, intervention details, outcome assessment tools and study outcomes. Any disagreements or discrepancies between reviewers were resolved by discussion or on review by a third author.

Data analysis
For the data analysis, we followed the recommendations of the Cochrane Handbook for Systematic Reviews of Interventions. 17 The analysis was performed using Stata version 16 (StataCorp LLC, College Station, United States of America). Pooled relative risks (RRs) are reported for categorical variables and mean differences for continuous variables, both with 95% confidence intervals (CIs). The standardized mean difference (SMD) served as a summary statistic when studies used different psychometric scales for assessing an outcome. 18 The SMD was calculated as the mean difference between the intervention and control group means in each trial divided by their respective standard deviations. 18 A fixed-effects metaanalysis (inverse variance method) was used to pool data and estimate effects. However, if the heterogeneity between studies was high (i.e. I 2 was greater than Box 1. Literature search strategy, meta-analysis of the maternal and paternal effects of kangaroo mother care for low-birth-weight and preterm infants, 1988-2023

Cochrane Library (330 records identified)
Search terms: For the Cochrane Central Register of Controlled Trials (CENTRAL) database, we used the pre-identified MeSH terms "kangaroo mother care method" and "kangaroo care" with no limitations on language or date of publication.

Web of Science (342 records identified)
Search terms: ((ALL = ("Randomized Controlled Trial" OR "controlled clinical trial" OR "Clinical Trial" OR randomized OR placebo OR "clinical trials as topic" OR randomly OR trial OR "Non-Randomized Controlled Trials as Topic")) NOT ALL = ((animals NOT humans))) AND TI = (("kangaroo mother care method" OR "kangaroo-mother care method" OR "skin to skin contact" OR "skin-to-skin contact" OR "skin to skin care" OR "skin-to-skin care" OR "kangaroo mother care" OR "kangaroo care" OR "kangaroo" OR "kangaroo holding")) AND Articles (Document Types)

Scopus (552 records identified)
Search terms: TITLE-ABSTRACT (("kangaroo mother care method" OR "kangaroo-mother care method" OR "skin to skin contact" OR "skin-to-skin contact" OR "skin to skin care" OR "skin-to-skin care" OR "kangaroo mother care" OR "kangaroo care" OR "kangaroo" OR "kangaroo holding") AND ("Randomized Controlled Trial" OR "controlled clinical trial" OR "Clinical Trial" OR randomized OR placebo OR "clinical trials as topic" OR randomly OR trial OR "Non-Randomized Controlled Trials as Topic") NOT (animals)) MeSH: medical subject heading; ti,ab: title, abstract. Note: The search was performed on 16 January 2023.

Systematic reviews
Kangaroo mother care and parental health Barsha Gadapani Pathak et al.
50%), 19 we used a random-effects model with the restricted maximum likelihood method. Egger's test was used to assess publication bias for outcomes reported in at least five studies.
The risk of bias in included studies was assessed using the revised Cochrane risk-of-bias tool for randomized trials (RoB 2) or the risk-of-bias tool for nonrandomized studies of interventions (ROBINS-I), as appropriate (Cochrane, London, United Kingdom). 15 The certainty of the evidence for the pooled estimates of outcomes was assessed using the GRADE approach. 14 Prespecified subgroup analyses were performed for: (i) the location where kangaroo mother care was initiated (i.e. in hospital or the community); (ii) the provider of kangaroo mother care (i.e. the mother alone, the mother supported by the father or the mother supported by other caregivers); (iii) the time of outcome assessment (i.e. when the infant was younger than 6 months, 6 to 12 months or older than 12 months); (iv) country income level (i.e. high, middle or low income); and (v) the type of outcome assessment scale.

Primary outcomes
Summary statistics for the effect of kangaroo mother care on primary study outcomes are shown in Table 2.
The pooled, mean maternal stress score was significantly lower among mothers in the kangaroo mother care group than among those in the control group (SMD: −0.82; 95% CI: −1.32 to −0.32; I 2 = 90.49%; 10 trials; 794participants; low certainty) at the latest followup a median of 30 days (IQR: 19-74) after childbirth (Fig. 4). In addition, the pooled, mean maternal anxiety score was significantly lower among mothers in the kangaroo mother care group (SMD: −0.62; 95% CI: −1.01 to −0.23; I 2 = 74.83%; six trials; 463 participants; low certainty) at the latest follow-up a median of 29 days (IQR: 7-120) after childbirth (Fig. 5). The pooled mean difference in maternal distress score, as assessed using the general health questionnaire, 51 between mothers in the kangaroo mother care arm and those in the control arm was −4.71 (95% CI: −9.77 to 0.35; I 2 = 0%; two trials; 100 participants; very low certainty) at the latest follow-up a median of 7 days after childbirth (Fig. 6).

Secondary outcomes
The pooled, mean, mother-infant attachment and bonding score was significantly higher for mothers in the kangaroo mother care arm than for those in the control arm (SMD: 1.19; 95% CI: 0.27 to 2.10; I 2 = 96.06%; nine trials; 450 participants; low certainty) at the latest follow-up a median of 52 days (IQR: 14-180) after childbirth (Fig. 7). Three trials reported the effect of kangaroo mother care on paternal health outcomes (Table 3). First, a randomized controlled trial in Sweden with 37 participants reported that 7.1% of fathers in the kangaroo mother care arm had depressive symptoms compared to 8.3% in the control arm but the difference was not significant. 35 That trial also reported a decrease in relationship problems with spouses. However, no difference in paternal stress scores was observed between the groups. Second, a quasi-randomized study in Israel with 146 participants reported that fathers in the kangaroo mother care group were more sensitive, less intrusive and showed higher reciprocity than those in the control group. 24 Third, a randomized controlled trial in Canada with 338 participants found that kangaroo mother care had a positive impact on the home environment and was positively correlated with the father's involvement in child care. 30  trials reported on additional maternal health outcomes, such as sensitivity, mood variance, confidence, satisfaction, duration of lactation, coping skills and sleep quality. Details are available from the online repository. 50 We did not find any reports on maternal or paternal physical health outcomes.
The subgroup analysis indicated that kangaroo mother care, whether given by the mother alone or by the mother and father together, can reduce maternal depressive symptoms and anxiety. Details are available from the online repository. 50 The beneficial effects of kangaroo mother care on maternal mental health outcomes seemed to be most prominent in the first 6 months after birth, and the effect was greater in lower-middle-income countries than high-income countries.

Discussion
Our meta-analysis included 30 trials from 18 countries that evaluated the effect of kangaroo mother care on the health of the mothers and fathers of 7719 preterm or low-birth-weight infants. We found high-certainty evidence that kangaroo mother care can substantially reduce the risk of moderate-to-severe, postpartum, maternal depressive symptoms. In addition, there was low-certainty evidence for a small or moderate decrease in postpartum, maternal depressive symptoms of any severity CI: confidence interval; IQR: interquartile range; MD: mean difference; ND: not determined; QRT: quasi-randomized trial; RCT: randomized controlled trial; RR: relative risk; SD: standard deviation; SMD: standardized mean difference. a The certainty of the evidence for the pooled estimates was assessed using the GRADE approach. 14 b The relative risk (RR) is the risk of the outcome in the kangaroo mother care arm versus the control arm with no kangaroo mother care. c The standardized mean difference (SMD) was calculated as the mean difference between the mean outcome scores in the kangaroo mother care and control groups in each trial divided by their respective standard deviations. d This figure corresponds to 14 (95% confidence interval: 2 to 25) fewer cases of moderate-to-severe postpartum maternal depressive symptoms per 1000 mothers. e The certainty was downgraded two levels because there was a serious risk of bias and serious inconsistency (i.e. I 2 = 83.41%; Egger's P-value: 0.0196). f The certainty was downgraded two levels because there was a serious risk of bias and serious inconsistency (I 2 = 90.49%; Egger's P-value: 0.0145). g The certainty was downgraded two levels because there was a serious risk of bias and serious inconsistency (I 2 = 74.83%; Egger's P-value: 0.1074). h The certainty was downgraded three levels because there was a serious risk of bias, serious indirectness (i.e. small sample size) and serious imprecision (i.e. wide confidence intervals). i The certainty was downgraded two levels because there was a serious risk of bias and serious inconsistency (I 2 = 96.06%; Egger's P-value: 0.012).  and in stress and anxiety, and for a small or moderate increase in motherinfant attachment and bonding. Verylow-certainty evidence from two trials indicated that kangaroo mother care reduced maternal distress, and evidence from three trials suggested it improved father-infant interactions.
No substantial effect was observed on paternal depression or stress, or on maternal or paternal physical health.
Our findings substantiate evidence from previous systematic reviews of the effect of kangaroo mother care on maternal health. A systematic review published in 2014 reported inconclusive findings on whether kangaroo mother care for preterm or low-birth-weight infants ameliorated negative maternal mood or promoted positive maternal and paternal interactions with the infant. 11 However, that review did not perform a meta-analysis. In 2019, a systematic review and meta-analysis reported that kangaroo mother care for preterm or low-birth-weight infants was associated with a 1.04% reduction in the pooled standardized mean depression score (I 2 = 82%; four trials) in mothers relative to the control group. 52 In addition, a 2021 metaanalysis reported that kangaroo mother care for premature infants significantly reduced the level of maternal anxiety (SMD: −0.72; 95% CI: −1.08 to −0.35; I 2 = 75%; six trials) and maternal stress (SMD: −0.84; 95% CI: −1.59 to −0.09; I 2 = 90%; four trials) compared with no kangaroo mother care. 13 However, that meta-analysis did not include studies involving low-birth-weight infants born at full term, and did not report other maternal or paternal health outcomes. Moreover, no previous metaanalysis assessed the overall quality of the evidence.
Our meta-analysis contributes to the existing literature by providing an up-to-date synthesis of the evidence from trials that evaluated the effect of kangaroo mother care for preterm and low-birth-weight infants on maternal or paternal health outcomes. We report pooled estimates for a wide range of outcomes, including postpartum maternal depressive symptoms, stress, anxiety, distress, sensitivity, mood variance and sense of competence and mother-infant attachment and bonding. Full details of our findings on the maternal sense of competence, with an interpretation, are available from the online repository. 50 Furthermore, the inclusion of 7719 infants means we were able to report primary outcomes with high statistical power, and coverage of a variety of low-, middle-and highincome countries means our findings may be widely generalizable. In addition, our evaluation of the certainty of the evidence in a quality assessment may be useful for framing future recommendations.
Although we did not find eligible studies on the effect of kangaroo mother care for preterm or low-birth-weight infants on maternal physical health outcomes, it is noteworthy that a metaanalysis from 2019 (six trials; 498 participants) 53 found that mother-infant skin-to-skin contact immediately after delivery of full-term infants with a normal birth weight was associated with a shorter third stage of labour

Fig. 4. Effect of kangaroo mother care on maternal stress, meta-analysis of the maternal and paternal effects of kangaroo mother care for low-birth-weight and preterm infants, 1988-2023
Study SMD (95% CI) in maternal stress scores between kangaroo mother care and control arms  Biologically, the beneficial effect of kangaroo mother care on the mother's mental health (i.e. less postpartum depression, anxiety and stress) could be explained by better mother-infant bonding and complex physiological mechanisms, potentially through increased oxytocin release. 54 It has been observed that mothers who have a prolonged separation from their infants due to neonatal intensive care admission or another issue are more likely to develop negative emotions such as despair and feelings of reduced competence and confidence. 52,55 Kangaroo mother care provides the mother and infant with an opportunity for close contact, which helps the mother gain self-confidence in caring for her premature infant. 40,56,57 Hence, the mother is more responsive to her child's needs, which improves the quality of the infant's attachment to its mother and family. 32 In addition, kangaroo mother care helps the baby recognize its parents. In the studies included in our meta-analysis, the duration of skin-to-skin contact varied substantially; the mean was 5.2 hours per day over 23 days in the postpartum period. Kangaroo mother care has also been associated with improved breastfeeding, 58,59 which is another trigger for oxytocin release and could be an alternative explanation for better health outcomes in mothers practicing kangaroo mother care. It is possible that the positive effect of skin-to-skin contact on mother-infant bonding may have facilitated the initiation of breastfeeding and encouraged exclusive breastfeeding.
The main limitations of our analysis were the high between-study heterogeneity and high risk of bias in 50% (15/30) of studies included. Although a predefined subgroup analysis was unable to identify the reason for the heterogeneity, it is possible the use of different assessment tools and time-points for quantifying mental health outcomes may have contributed. Nonetheless, the findings of the subgroup analysis should be interpreted with caution because the subgroups contained relatively few studies or participants and, consequently, effect size estimates may be imprecise.
In conclusion, kangaroo mother care is known to benefit preterm and low-birth-weight infants. Our study provides comprehensive, up-

Fig. 5. Effect of kangaroo mother care on maternal anxiety, meta-analysis of the maternal and paternal effects of kangaroo mother care for low-birth-weight and preterm infants, 1988-2023
Study SMD (95% CI) in maternal anxiety scores between kangaroo mother care and control arms    The home environment was more stimulating and involved greater caregiving in the intervention arm than in the traditional care arm, which was positively correlated with the father's involvement CI: confidence interval; EPDS: Edinburgh Postnatal Depression Scale; HOME: Home Observation for Measurement of the Environment; IQR: interquartile range; ND: not determined; RCT: randomized controlled trial; SD: standard deviation; SPSQ: Swedish Parenthood Stress Questionnaire.

Systematic reviews
Kangaroo mother care and parental health Barsha Gadapani Pathak et al.
to-date evidence that it can also have a positive effect on maternal mental health outcomes, such as postpartum depression, anxiety, stress and distress, and on mother-infant bonding. We found limited evidence that kangaroo mother care has a beneficial effect on father-infant interactions, but no clear effect on paternal depression or stress was observed. Although our review findings are applicable to the mothers and fathers of low-birth-weight and preterm infants globally, including those in low-and middle-income countries, caution is warranted as the certainty of evidence ranges from high to very low. Nevertheless, our findings address an important knowledge gap and could help support the promotion of kangaroo mother care as an intervention that can enhance maternal health in the postnatal period as well as improving the infant's health. Further research is needed to clarify the effect of kangaroo mother care for vulnerable preterm and low-birth-weight infants on maternal physical health and on paternal health, and to explore the possible biological mechanisms underlying its beneficial effects. ■

Acknowledgments
We thank Shuchita Gupta and Rajiv Bahl at WHO and members of the WHO Department of Maternal, Newborn, Child and Adolescent Health. Bireshwar Sinha is also affiliated with the DBT/ Wellcome India Alliance, Hyderabad, India and the University of Tampere, Finland. Barsha Gadapani Pathak is also affiliated with the University of Bergen, Norway.
Kangaroo mother care and parental health Barsha Gadapani Pathak et al.

Systematic reviews
Kangaroo mother care and parental health Barsha Gadapani Pathak et al. Birth Questionnaire -mother subscale); and (ii) home environment and quality (HOME tool) 12 months (i) Mothers in the intervention arm created a more stimulating and better caregiving environment for their child than mothers in the control arm; (ii) there was a positive correlation between the quality of the environment and the father's involvement; and (iii) the family environment of male infants was improved most by kangaroo mother care.